1. Field of the Invention
The invention generally relates to method of and apparatus for obtaining fingerprint information about structures of materials and, more specifically using a spatial frequency spectrometer for and method of detection of spatial structures in materials.
2. Description of the Prior Art
Spatial frequency spectrum may be considered to be able to yield fingerprint information about the surface and internal structures of samples. It can provide spatial information from the periodic, aperiodic, and random structures of the sample from the spatial intensity distribution. A spatial spectrum can be formed given the dominating spatial variation within and on the surface the material. Here, we teach the use of spatial frequency to form a spectrum to obtain information on the internal structure of materials such as tissues-human and animal state, paper goods as money, mail, gems (diamonds defects and quality), and art forms to form a spatial spectrum of a material form in cm−1. The spatial spectrum can yield spatial coherent information from the periodic and random structures of the material. It is well known that a focal-Fourier plane with light intensity distribution is composed of “spatial frequencies” which is similar as the way that a time domain signal is composed of various frequencies [1]. The spatial frequency can be obtained by a Fourier transform analysis of the light intensity distribution which and how many frequencies are contained in the waveform in terms of spatial frequencies for unit of cycles (cy) per unit distance (cm−1). These frequencies can be addressed by Fourier decomposition, which is analogous to temporal frequencies in cycles per second for in time-domain. The light can arise from elastic scatter, fluorescence, and Raman images of the material. The teachings laid down the foundation for a Spatial Frequency Spectrometer to determine the emitting spatial structure of the material.
An example of the spatial spectrum of a material is the comparing different tissue types. Tissue can be normal, benign, dysplastic (precancer) and cancers. Spatial frequency can reveal the different states. Cervical dysplasia, e.g. Cervical Intraepithelial Neoplasia (CIN), is the potentially premalignant and abnormal squamous cells on surface of cervix [2]. Although not a cancer, above 12% of CIN cases progress to become cervical cancer if left untreated [2]. Others cause warts. Cellular changes and disorder of tissue structure are associated with the stages of CIN, which is classified in three grades [2]. Usually cervical tissue has order and well-defined cell structure in its normal stage [2]. When cancer starts, the tissue becomes distorted, random, and structure-reducing. The current techniques for CIN include the Papanicolaou or “Pap” smear and colposcopy. However, to make a definite diagnosis of cervical dysplasia, a biopsy should be taken of any abnormal appearing areas [2]. The different types of skin cancer from ABCD can be revealed in the spatial frequencies from the structures of melanoma and basal carcinomas.
Another example for spatial frequencies where structures are apparent is in paintings. A paint of different artist strokes are different and can be used to show different characteristic spatial frequency pattern with unique spatial patterns. Also, different artist paintings can show how painter strokes (right handed and left hand) can be detected as a second example on the use of spatial structure. The salient properties associated with light and photonic laser technology in the visible-NIR can be used to locate these blind blisters so that the difference areas can be identified between the art of a masterpiece and forgery art form and from the spatial frequencies in the spectrum.
Photonic measurements and images from scatter and emission processes can be used in the visible-NIR using the ultimate light called the Supercontinuum, lamps, LEDs and lasers and spatial frequency to scan the surface of paintings and other textured art works to determine if the brushworks or the signatures are by the original artist. We also know that this Photonic technology will detect areas that may be over-painted either by the artist or in an earlier restoration. There are spatial variations in paper on nm scale from fibers, different currency and denominations have native or intrinsic spatial variations and can be implanted with a spatial code within. Diamonds have defects that can provide a code for a stone or gem.